1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to digital broadcasting transmission and reception, and more particularly to digital broadcasting transmission and reception devices that can provide a sub-channel to transmit and receive robust stream, and methods thereof.
2. Description of the Related Art
Advanced Television System Committee (ATSC) Vestigial Sideband (VSB) system, which is an American terrestrial digital broadcasting system, is a single carrier system, and uses field sync with 312 segment units. Accordingly, this system has inferior reception performance in a deteriorated channel, particularly, in a Doppler fading channel.
FIG. 1 is a block diagram of a conventional ATSC VSB system, and FIG. 2 is a view illustrating a frame structure of a conventional ATSC VSB data.
FIG. 1 shows the Enhanced VSB (EVSB) system proposed by Philips Electronics, which forms and transmits a dual transport stream by adding robust data into normal data of a conventional ATSC VSB system.
A conventional digital broadcasting transmission process will be explained with reference to FIG. 1. A data randomizer 11 randomizes a dual transport stream, a Reed-Solomon (RS) encoder 12 adds a parity to the dual transport stream to correct errors, an interleaver 13 interleaves the RS encoded data, and a trellis encoder 14 trellis-encodes the interleaved data.
A MUX 15 inserts field sync and segment sync into the error correction coded data to multiplex the data, and a modulator 16 up-converts the data into a signal in an RF channel bandwidth to transmit it.
A conventional digital broadcasting reception process will be explained with reference to FIG. 1. As a tuner (not shown) down-converts the RF signal into a baseband signal, a demodulator 21 detects and demodulates the baseband signal, and an equalizer 22 compensates for a channel distortion.
Then, a Viterbi decoder 230 corrects errors and decodes symbol data, a deinterleaver 24 rearranges data distributed by the interleaver 13 of the transmitter, an RS decoder 25 corrects errors, and a de-randomizer 26 de-randomizes the error-corrected data to output MPEG-2 transmission stream.
FIG. 2 is a view illustrating a VSB data frame of ATSC VSB system, in which segment field sync and field sync are inserted. As can be seen from FIG. 1, one frame comprises two fields, and one field comprises one field sync segment and 312 data segments.
In the VSB data frame, one segment corresponds to one MPEG-2 packet, and one segment comprises four symbols for segment sync and 828 data symbols.
The segment sync and the field sync are used for synchronization and equalization of a digital broadcasting receiver. In other words, the segment sync and the field sync are already known data between the digital broadcasting transmitter and the digital broadcasting receiver, and are used as reference signals for the digital broadcasting receiver to perform equalization.
As described above, major problems of the conventional VSB system, which transmits and receives data over the air, are performance degradation in weak signal strength and dynamic multi-path interference. The conventional ATSC VSB system illustrated in FIG. 1 transmits a dual transport stream including robust data; however, it cannot be expected to improve degraded reception performance in a multi-path channel when the conventional VSB system transmits normal data stream. Additionally, there is no big improvement in the reception performance regarding robust stream in a multi-path environment.